Samsung Galaxy Trend Plus (S7580), this includes Android lollipop roms, Kitkat ROMs as well as Marshmallow based custom ROMs i.e., CM11, CM 12.1 and CM13.Now you can easily downgrade of Update your device to lollipop, marshmallow, and KitKat.
Before starting to make sure you have a custom recovery installed on your device I recommend you to install TWRP recovery because you can install, Make backup quickly.These roms may have some bugs so don’t expect it to be totally stable as these roms are unofficially provided by different devs.
#How to install Custom Rom for S Duos 2
Follow below guide on how to install Android marshmallow 6.0 by flashing CM13 rom on your device.
1.Download desired Rom for your device and the appropriate Gapps 6.0/5.1 package from the link given below link.
2.Now place the rom and gapps.zip file in sd card.
3.Now reboot into TWRP Recovery mode
4.Then flash the rom and gapps from the recovery in it.
5.Now Clear Cache and Clear Data.
6.Reboot your device.